British authorities have now recognised the fact that economy-class syndrome does exist, and affects those in first class as well (quite the equilliser!!)
British airlines will now have to include this sydrome in their pre-flight safety briefings, and what exercises can be done to prevent it, along with keeping away from alcohol. On long haul flights all air-packs will have to be switched on.
BTW-it is the development of blood clots within the veins, and leads to heart-attacks.

"Economy class syndrome" is caused by deep vein thrombosis. This means a build-up of clotted blood often caused by being cramped for long periods of time.
When this blood-clot reaches a vital organ, such as the heart, the effects can end in death. Thousands are thought to die every year.

It is thought however that a few minutes of exercise each hour and streaching your legs occationally will stop a clot forming.

Britannia already makes anouncements advising passengers to do the above. BA and Virgin Atlantic are having tests done to see how such deaths can be prevented.